Bob just filled his car's gas tank with 20 galions of gasohol, a mixture consisting of 5% ethanol and 95% gasoline. If his car runs best on a mixture consisting of 10% ethanol and 90% gasoline, how many gallons of ethanol must he add into the gas tank for his car to achieve optimum performance?

$\sec A+\tan A=\frac{5}{2}$ হলে $\sec A-\tan A=?$

A and B invest in a business in the ratio 3:2. If 5% of the total profit goes to charity and A's share is Tk. 855, total profit is _?

Find the missing number in the series 3, 6, 18, 72, 360, _

If a boy takes as much time in running 10 min. a car takes in covering 25 m, the distance covered by the boy's during the time the car covers 1 km is?

Shima has $\frac{4}{5}$th of a tank of fuel in his car. He uses $\frac{1}{10}$th fraction of a tank per day. How many days will his fuel last?

The length of rectangle ABCD is $\frac{6}{5}th$ of it's breadth. Its perimeter is 132. What is it's area?